Method of making adhesive tape



March 23, 1954 E, 1 H|CKOX METHOD OF MAKING ADHESIVE TAPE Filed Deo. 28, 1950 l @Il Q HU( kv 5 Patented Mar. 23, 1954 r-2,672,978 METHOD OFMAKIN G ADHESIVE .TAPE Elmer LI. /Hic'k'ox,:W'arren, lOhio, Aas'sigin'nto General Motors Corporation, Detroit,'Mich., a cor- ;poration of Delaware Application December 28, 1950, SerialNo. 203,127

3 Claims. I1 *This inventionrelates generally to the problem Wrapping of an article Ywith tapeor rto the Wrapping-of a group of elements with tape to hold such elements assembled together, for exa the heating chamber is opened and as -soo'n'astne temperature therein drops suiiiciently, the racks holding the rolls of tape are removed and the ple, tothe taping of wires to form 'an assembly 5 rolls are cooled in the room to room temperature. commonly known aswiring harness, such vas used There are various thermoplastic materials in automotive vehicles for connecting the genwhich can be used in carrying out applicantf's erator With the storage battery and other current method and While the heating of the rolls of t'a'p'e consuming devices, and more particularly to a is preferably effected by/use of steam, a' hot air method of making an adhesive tape which is suitoven can also be used and, in fact, actually-has able for this purpose. been used with satisfactory results.

Taping has previously been effected by the use Further objects and advantages of the 'present of pressure sensitive tape, known as friction tape, invention will be apparent froml the followingfdeobtained in rolls, the convolutions of which adscription, reference being had to the accompanyhereto such extent that, when the peeling oir ing drawings in which a preferred embodiment'o'f of the free end is started, the weight oi the roll an apparatus for carrying out the methodof the can be supported by the free end without causpresent invention is shown. ing'the roll to unwind. The free end portion In the drawings: having been pressed against the hunched wires Fig. 1 is an end View of a rack loaded with s0 that the unwound roll may be supported by 20 rolls of tape to be heated and shown ywithin a the wire, taping is continued by tossing the roll circle representing the inside wall of a steam about the wires. One variety of friction tape 'heating chamber. which can be obtained is athermoplastio materiel Fig. 2 is a fragmentary side view of the rack such as Vinylite, which has been prepared with Showing some of the rolls of tape Supported an adhesive surface so that the convolutions of thereon. a roll of such tape will adhere together. The apparatus for slitting a sheet of suitable The primary object of this invention is to promaterial into strips of the desired widths as it vide a method of and apparatus for making a is drawn from a supply roll and for simultanesuitable tape which can be employed to wrap the ously forming rolls of the strips so formed is wires of a wiring harness or other elements, from not Shown herein and any Suitable apparatus for sheets of a thermoplastic material, .to the surface unwindng a Sheet of thermoplasticmaterial from of which no adhesive compound has been applied a supply roll slitting such material into strips of and the surface of which has not been treated suitable width and winding such strips into rolls in any way. According to the present invention, while maintaining the strips of material under this object is accomplished by unwin'ding a sheet 35 suitable tension can be used. In other words,lthe of suitable thermoplastic material from a supspecific construction of the apparatus which is ply roll, slitting the material as it is unwound employed to form the rolls of tape is'not material from the supply roll to form strips of whatever and not a part of the present invention. In width may be desired and simultaneously windcarrying out applcants method, the T0115 0f tape ing vsuch strips on hollow cores of paper or other 40 as fOImBd by 50m@ Suitable apparatus are suitable material while the strips are under tenadaptedto be placed on a rack which is` mov-able sion, so vas to provide rolls of tape of a size bodily into a heating chamber in order to efsuitablefor handling and in which the convolufect the desired heating of the rolls Oftape sup'- tions offtape are under appreciable tension. ported therein, such rack being described here- `A quantity of these rolls are placed in proper inafter. ly spaced relation on rods which are placed upon The reference numeral l0 designates 'the rack a rack in such spaced relation as will enable in its entirety andsuch rack comprisesangle iron the-rolls to be heated most uniformly. The loaded end frames! {,joined at their lower ends-byangle rack is placed in a suitable heating chamber and IODS l2 Which are COIlIleCted by angles I3. 4Ali the rolls of thermoplastic strips are heated. the top, the frames!! are connected by two paral- When heated at the proper temperature and for lel angle irons M which are connected with a sufficient period of time, the surface ofthe tape notched blocks l5 which are adapted to receive becomes suiiiciently adhesive to cause the adjachain hooks of a hoistfor moving'therack. The cent convolutions of each roll of tape toadhere frames Il support a plurality of vertically spaced so as to permit the Wrapping of the tape around angle irons I6 to each of which is welded a bar I 1 the wires of a Wiring harness or other elements having notches lfor receiving rodsle Whichare to be carried out in the manner described above, adapted to support rolls of tape designated at 20 the tape in the roll being sufliciently adhesive to and which, when mounted on the rods 19, .are support the roll of tape without permitting it to spaced-apart a suitabledistance. "Theangle irons unwind. eo I6 preventany appreciablefendwise movementycf kAfter :the I,rolls of tape Ahave been heated at theproperttemperature-fcr the necessary period the rods I8 :so that ,they willnot :be disengaged from' the supporting notches l-B whentherodsare 3 placed on the rack, and the notches are so spaced longitudinally of bars l1 that when all of the notches are occupied by bars i9 the rolls 20 will be located in rows positioned as indicated in Fig. 1.

As already indicated, the rolls of tape 20 are formed by Winding strips of thermoplastic tape under tension, as they are received from a sheet slitter, upon hollow cores or tubes 20c of paper or other suitable material, which are placed on and rotated by a winding mandrel which is rotated to draw the thermoplastic material from a supply roll and to effect the slitting of the sheet of material carried by the supply roll into tape of suitable widths.

In forming the rolls, a sheet of suitable material is unwound from a supply roll, is slit into strips of suitable widths as it comes oil the supply roll and the strips of tape so formed are wound into rolls. The apparatus employed is provided with some suitable means to place the tape under tension as the rolls are formed. The tension on the tape as the rolls are formed is enough to slightly elongate the material during the formation of the rolls so that after the rolls are formed the tape tends to contract, thus increasing to some extent the compression between adjacent convolutions of the rolls. Of course, the greater the elongation, the greater will be the compression force which is created. It has also been found that there is some variation in this force, it being greater some distance within the roll than near the finish end, but this Variation is not sufcient to be of any material importance.

Also there is some variation in tension of the tape in rolls formed from diiierent sheets of material. For example, the material in one supply roll may have a smoother surface than that in another and the roll of smooth material unwinds less easily than a roll with rougher material. These variations in tension are not very great, but it has been found that by modifying the time and/or temperature of the heat treatment of the rolls o tape, which will be described later, the effect of any variation in the tension of the tape in the rolls can be substantially eliminated so that a tape of substantially uniform character can be produced.

The tension on the tape during the formation of the rolls is not suhicient to cause any appreciable permanent elongation of the strips of tape, but is always enough to eliminate wrinkles and to bring about the desired degree of adherence between the adjacent convolutions of the rolls to be obtained when the rolls are heated. The winding operation is continued until the rolls have a suitable diameter, for example, a 4 inch diameter for tape 3A to 1 inch in width, and a 41/2 inch diameter for tape of 11/.1c to 11/2 inch width. The inside diameter of the cores 20o on which the strips of tape are wound is such that the cores fit loosely on rods I9 which may be of 1/2 inch diameter, for example.

The rack I0, when loaded with the coils of tape to be heated, is elevated by a hoist which is not shown, placed on rollers 2l and positioned within a heating chamber, the inside wall o'f which is indicated by the circle 22. This chamber may be a steam vulcanizer of conventional type. The door of the vulcanizer is closed when the loaded rack is positioned therein and the steam is then turned on full to the steam controller and a hand valve is opened until steam is seen issuing from the bleeder valves of the vulcanizer. The steam supplied to the vulcanizer is under the control of an automatic control means which limits the temperature to that desired and maintains the temperature at that value. The heating of the rolls can be effected by subjecting them to the effect of steam at 212 and under no pressure, if the heating operation is carried out for a sufcient period of time and good results have been also obtained if the rolls are heated for a somewhat lesser period of time at a steam pressure of 2 to 41/2 pounds and temperatures in excess of 212 F., for example 218 to 225 F. However, the best and most uniform results have been secured by subjecting the rolls in the vulcanizer to the action of steam at atmospheric pressure and 212 F. for a period of approximately 15 minutes, then raising the steam pressure to a pressure of 2 to 4 pounds, with consequent raise in temperature, and continuing the heating cycle for approximately another 15 minutes. This part of the cycle may be varied to some extent when different thermoplastic compounds are used so as to produce substantially the same degree of adhesion with the different compounds.

As soon as the heating operation is completed, the steam is shut off and the drain valve of the vulcanizer is opened and as soon as possible after the steam pressure has dropped to Zero the vulcanizer is opened, the rack with the heated rolls thereon is removed from the vulcanizer so that the tape rolls may be ultimately cooled by the surrounding atmosphere to room temperature. When the rolls are sufliciently cooled, they may be removed from the rack and may be used immediately or stored for future use as the surface of the tape remains adhesive for a long period of time, if the rolls of tape are not unwound, although the surface of the tape does not at any time feel sticky or tacky to the touch.

The heating of the rolls of tape can be carried out at even higher temperatures if the heating time is suitably reduced and satisfactory results obtained, but as stated, the best results have been obtained by heating during the iirst part of the heating cycle at 212 F. and during the second part of the cycle at a temperature of 218 to 225 F. It will be further understood that instead of employing a steam vulcanizer, the loaded rack could be placed in a suitable hot air heating oven heated either electrically, or otherwise, and if such oven is maintained at the proper temperature for the desired period of time satisfactory results could be obtained. In other words, although, according to the present method, the heating of the rolls of tape is preferably effected by use of a steam vulcanizer, the use of the latter is not essential and the heating of the rolls can be eifected by other means with good results.

The invention is not limited to the use of any one thermoplastic material. Good results have been obtained with diierent materials all of which are compounds of polyvinyl chloride resins with certain plasticizers and stabilizing agents. These materials are obtainable on the market and have substantially similar characteristics. For example, one form of such a compound which has been used with very satisfactory results is known to the trade as Vinylite, while another compound of Similar character which has also been used with success is known to the trade as Geon. These materials are obtainable in relatively thin sheets for example the Vinylite which has been used has a thickness of .013 and .G09 of an inch. Other thermoplastic materials, the surfaces of which will become suciently sticky or tacky to cause adjacent surfaces of such material to adhere together with appreciable force the tape.

if heated at a suitable temperature for the proper time while such adiacent surfaces are held together under a slight pressure, can be employed. Examples of these are materials which include polyvinyl acetate polyethylene.

When rolls of tape are heated in accordance with the present invention, the tape does not have any pronounced adhesiveness to the surface of the cable in the norm-a1 sense, such as ordinary friction tape would have and, therefore, is not adhesive tape in the ordinary sense. However, the tape layers or convolutions stick tight to each other until forcibly unwound from the roll, and it has been found that tape treated in accordance with the present process can be used to wrap the Wires of a wiring harness. or for other purposes, as successfully as tape to which some adhesive compound has been applied to the surface, as for example, ordinary friction tane. The principal advantage of the rftethod which constitutes the present in"ention is to obtain a roll of tape which reduires the application of appreciable force to unwind it from the roll which is formed, so that it can be used in the manner in which conventional friction tape is ordinarily used to wrap a wiring harness by tossing the roll around the harness after the free end o'l the tane is pressed against the harness and without applica tion of any adhesive substance to the surface of After the wrappingr of the harness is completed, the nish end of the tap-e is usually fixed in place by taking a hitch in the tape and the taped harness may then be placed in a vulcanizer which causes the tape wrapping to be permanently bonded. However, this is not necessary and the tape is sometimes used without carrying out the step of heating to effect bonding.

As already indicated, the tape when wound on the rolls is under some degree of tension. Some tension is necessary in order to cause the adjacent tape turns to adhere to each other when subjected to heat treatment and the greater the pressure, the greater the degree of adhesiveness for any given temperature. It has been actually found that if the tape rolls are supported on edges, the portion of the tape adjacent the support shows greater adhesion, due solely to the relatively slight weight of the roll, than do other portions of the roll more remote from the support, during the heat treatment. Since uniform Y adhesion in the roll is most desirable, the rolls are supported during the heating operation by rods which run through the cores on which the rolls are wound. Also in order to produce uni.- formity in the adhesiveness of the tape, it is important to effect uniform heating since variations in application of heat would also produce variations in the adhesiveness of the tape. To this end the rolls are evenly spaced on the supporting rods I9 and the rods are also so spaced that steam can readily pass between all of the rolls of any single row and all of the rows of rolls as well, the rods I9 being arranged about an unoccupied space of substantial size at the center of the heating chamber 22, whereby the steam has more ready access to all of the rolls of tape in said chamber.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. The method of forming a roll of adhesive tape from a thermoplastic material consisting essentially of a plasticized polyvinyl chloride resin, which includes the step of heating a roll of tape formed of such material while under tension, by subjecting the roll of tape to the heating effect of steam at 212 F., and atmospheric pressure, for approximately 15 minutes and for subsequently subjecting the roll of tape to the heating effect of steam at 2 to 4 pounds pressure and at a temperature of 218 to 225 F. for substantially the same period of time, sov as to cause the surface of the tape to become sufliciently adhesive to adhere to the surface of adjacent convolutions with enough force to require application of appreciable force to unwind the tape, the heating temperatures and the time of heating being insuicient to effect fusion of the tape.

2. The method of forming adhesive tape from a thermoplastic material consisting essentially of a plasticized polyvinyl chloride resin, which includes the steps of forming rolls of tape in which the tape is under appreciable tension. from sheets of thermoplastic material of suitable thickness, placing a plurality of such rolls of tape within a closed heating chamber into which steam may be introduced for heating purposes and positioning such rolls within the chamber in such a way that steam may pass adjacent all the rolls and the heating effect thereon is substantially equalized, introducing steam into said chamber at substantially atmospheric pressure for approximately 15 minutes in order to maintain in the heating chamber a temperature of substantially 212 F. and subsequently introducing steam into said heating chamber at a positive pressure of 2 to 4 pounds for approximately 15 minutes in order to A maintain in the heating chamber a temperature in excess of 212 F. whereby the surface of the tape is caused to become suiiiciently adhesive, to adhere to the surface of the adjacent convolutions of theroll with enough force to require the application of appreciable force to unwind the tape from the roll, the degree of heat to which the tape is subjected being insufficient to fuse the adjacent convolutions of the roll, whereby the roll may be unwound without damage to the tape by the application of sufficient force thereto.

3. As an article of manufacture, a roll of tape in which the adjacent convolutions of the roll adhere in a non-fused relationship sufficiently to withstand unwinding due to the suspended weight of the roll itself, said tape being formed solely of a thermoplastic material consisting essentially of a plasticized polyvinyl chloride resin the surfaces of Which are made adhesive by the limited application of heat, said convolutions being under a predetermined pressure due to elastic deformation of said tape during assembly.

ELMER J. I-HCKOX.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,930,995 Carroll Oct. 17, 1933 y 2,093,087 Lynn Sept. 14, 1937 2,119,163 Herrmann et al. May 31, 1938 2,219,700 Perrin et al Oct. 29, 1940 2,395,668 Kellgren et al Feb. 26, 1946 2,406,127 Alfthan Aug. 20, 1946 2,553,816 Ebel May 22, 1951 FOREIGN PATENTS Number Country Date 440,776 Great Britain Jan. 6, 1936 

3. AS AN ARTICLE OF MANUFACTURE, A ROLL OF TAPE IN WHICH THE ADJACENT CONVOLUTIONS OF THE ROLL ADHERE IN A NON-FUSED RELATIONSHIP SUFFICIENTLY TO WITHSTAND UNWINDING DUE TO THE SUSPENDED WEIGHT OF THE ROLL ITSELF, SAID TAPE BEING FORMED SOLELY OF A THERMOPLASTIC MATERIAL CONSISTING ESSENTIALLY OF A PLASTICIZED POLYVINYL CHLORIDE RESIN THE SURFACES OF WHICH ARE MADE ADHESIVE BY THE LIMITED APPLICATION OF HEAT, SAID CONVOLUTIONS BEING UNDER A PREDETERMINED PRESSURE DUE TO ELASTIC DEFORMATION OF SAID TAPE DURING ASSEMBLY 